U.S. Ser. No. 274,070, entitled High Coercivity Rare Earth-Iron Magnets and assigned to the assignee hereof, discloses novel hard magnet compositions and the method of making them. More specifically, it relates to alloying mixtures of one or more transition metals and one or more rare earth elements. The alloys are thereafter quenched from a molten state at a rate such that they solidify with substantially amorphous or extremely fine grained crystalline microstructures (as determinable by ordinary X-ray diffraction techniques) and have room temperature intrinsic magnetic coercivities after magnetization of at least about 1,000 Oersteds. The preferred transition metal for the magnet alloys is iron, and the preferred rare earth elements are praseodymium and neodymium. These constituents are preferred because of their relative abundance in nature, low cost, as well as inherently higher magnetic moments.
Because the usefulness of a hard magnet is a direct function of its strength, I have looked for a means of increasing the intrinsic coercivity and energy product of these and other substantially amorphous rare earth-transition metal (RE-TM) hard magnet compositions. I have also looked for a way to increase the relative iron content of amorphous rare earth-iron (RE-Fe) magnet alloys without sacrificing intrinsic coercivity. Higher iron concentration is desirable because of reduced alloy cost and improved magnetic energy product. I have also sought a way of increasing the temperature at which such magnet compositions retain their hard magnet properties.
Accordingly, it is an object of the invention to provide substantially amorphous or extremely fine grained rare earth-transition metal hard magnet compositions with improved intrinsic magnetic coercivities and energy products, even at elevated temperatures. A more particular object is to add a small amount of the element boron to known, substantially amorphous, magnetically hard rare earth-transition metal compositions to improve their intrinsic coercivities, energy products and increase their Curie temperatures.
Another object is to make hard magnet alloys by melting and rapidly quenching mixtures of one or more rare earth elements, one or more transition metal elements and boron so that the alloys exhibit high intrinsic coercivities and energy products. A more specific object is to make such high strength magnet alloys from iron, boron, and lower atomic weight rare earth elements, particularly neodymium and praseodymium. Another object is to make these magnetically hard alloys by melt spinning or a comparable process.
Yet another object of the invention is to provide a means of increasing the relative iron content of rare earth-iron alloy compositions without untoward loss of intrinsic coercivity. More particularly, it is an object to add an amount of boron to a magnetically hard, amorphous alloy of low atomic weight rare earth elements and iron sufficient to improve and stabilize its inherent intrinsic magnetic coercivity and energy product. Another particular object is to increase the residual magnetism of such high coercivity alloys by increasing their iron content.